Photoelectric electronic tube



Sept. 22, 1942. P. H. CRAIG Erm.

PHOTOELECTRIC ELECTRONIC TUBE Filed Mayl 13, 1940 2 Sheets-Sheet l INVENTOR. a/g /747 an sept. 22, 1942. P. HCR/G mi. 2,296,269

' `PHOTOELECTRIG ELECTRONIC TUBE y Filed May l5, 1940 2 Sheets-Sheet 2 Opaque G/Qss /V' H H U BY @www Patented Sept, 22, 1942 -uNlTlazD STATES PATENT oFFlcE A l .y l 2.29amY t p e VPalmer H. Craig, lShaker Heights, and Lester C.

Herman, South Euclid, Ohio, assignors to Invex Corporation, a corporation of New York Application May is, 1940, serial No. 334,846 14 claims. (ci. 25o-41.5)

invention relates to photo-electric electronic tubes.

Heretofore photo-electric electronic tubes have been proposed of two general types. type, light sensitive material that is to say, material which when it is exposed to light emits electrons, is`V provided in an envelope, and the ow of these light-emitted electrons themselves toward a positive electrode in the tube provides the main current through the tube, externally available for use. In the other type, the tube is of the general class of space discharge tubes,

`andthe electrons emitted `from the light-sensi-v tive material, start the ow of discharge current through the tube.

In the rst type of tube the external current In One is small because of the low light-effected emisf sion of electrons; and in the second type of tube the external currentis smallbecause the current flow producing potential on the main electrodes must be kept to a low value to prevent dis-V charge current from ilowing independently of illumination of the light-responsive material.

Because the amount of current made available by such prior tubes `when subjected to light is so small, it follows that in most `of the practical applications in which light controlled electric power is wanted,` the current output of such tubes must be amplined by auxiliary apparatus'. 'I'he photo-electric tube of the present invention is per se, a "power tube" of the gaseous discharge type, capable ofconducting as much current as such a tube conducts when used as an ordinary power tube, limited 'infact only by the1 maximum` permissible temperature rise thereof; and the present invention comprises vmeans by which the current now between the anode and cathode of such a power tube may `be caused to. attain its full capacity value, or

optionally any fractional part thereof, bythe action of corresponding dilerent intensities of light.

The photo-electric tube of the present invention therefore fis, inv the true sense, a photoelectric power tube, and we therefore designate it and` distinguish ,it` from `prior photo-electric tubes by the name Photodyne,

While the principle underlying our invention may be variously applied `in the photo-electronic art,`we have chosen for' the purposes of this specification to illustrate and describe it as embodied in a space discharge power tube of the rectifier class, and comprising an envelope containing ionizable gas and an anode and a `hot cathode, and -having a control electrode or grid.

In such as gaseous rectifier tube, discharge current flows only from the cathode to the anode and only when the anode is positive with respect to the cathode; and herein reference to the anode construction of cathode comprises, in various forms, metal coated with thermionic material and indirectly heated by an incandescent lament. The electrons emitted by the` heated thermionic coating, together with the electrons produced thereby by ionization of the gas in the envelope, and owing toward the positive anode, constitute the discharge current, (or the path therefor if the current by considered as flowing frornthe anode as is the conventional fiction). Representative of such thermionic coatings are barium oxide and strontium oxide.

In the well known process of evacuating the envelope of a rectier tube having such a cathode, the cathode is heated, and some of the thermionic `material thereof` becomes vaporized and ycondenses ,on the inner'A surface of the envelope in a `film of thermionic material, so that in an indirectly heated cathode rectiiier when nished, the greater part of the thermionic-material remains on the cathode, but a thin lm of the same is in the form'of a deposit on the envelope wall. e

Also at the end of the evacuating process, a

so-called getter is employed comprising a metal` the envelope in a thin fllm' The getter may be located at one endof the envelope, in which case the getter iilm will form at the corresponding end portion of the envelope. The film consists of metals, `and metal oxides, "nitrides, carbonates,

etc.,`determined by the getter and theoxygen,

nitrogen, carbon dioxide, etc.,' which may be present inthe envelope when the getter `is ashed. Representative of such getters is a mixture oi 25% barium, 20%. aluminum, and`55% magnesium in powdered form.

The ionizable gas in the envelope of such tubes Y 'A is introduced after evacuationI and representative 'of such gases is argon.

Now we have discovered that if a hot cathode rectifier of this'class when constructed as hereinafter described and evacuated and containing' argon (at suitable pressure, to b e referred to) and t having a film or films on. thelinner wall of the envelope as described, has its grid energized with a negative potential to the degree which just pre vents current flow between the anode and cathode, for a given potential between the anode and cathode, the tube is photo-electric. That is to say, if light falls either upon the thermionic coating of the cathode, or upon the condensed thermionic coating, or upon the condensed getter coating on the envelope inner wall, the grid is thereby rendered inelective to prevent the current flow; and current flows between the cathode and anode, and furthermore, flows in amount corresponding with the intensity of the light falling an either of the said coatings; and in correspondence with variations of the intensity of the illumination of the coating, the current flow varies. from very small amperage up to and including .the maximum amperage capacity of the said coatings be exposed to light, the grid is there-4 by rendered ineffective to maintain the flow and the current flow is interrupted or is reduced commensurably with the intensity of the light.

The tube of this invention responds to light as stated above, when the grid is inside the envelope, between the cathode and anode, but we prefer to employ an outside band-grid, encircling or embracing the outer wall of the envelope, such bandcontrol electrodes being well known and being described in the patent to Palmer H. Craig, representative of which is Patent No. 42,001,836, issued May 21, 1935. r

We are not, at the present time, certain as to the exact nature of the above described phenomenon, or the full explanation thereof. Obviously, the aforesaid response of the tube to light is not dependent upon the use of so-called light-sensicharge or field produced by the grid which controls the amperage flow through the tube; and that electrons or photons are emitted from the said coatings when subjected to light and that they neutralize or drain -ori' or short circuit the said electro-static charge or field, .thus destroying or reducing it (commensurably with the'intensity of the light) and correspondingly changing the eiect of the grid upon the current flow through the tube. This is evidenced by the fact that the eiect of the grid can be varied by diverting or by-passing some of the grid energization by means of a rheostat disposed externally of the envelope and paralleling the grid, as We have found by experiment.

As illustrative of the light responsiveness of tubes embodying .the principle above described we have found that a tube having a continuous carrying capacity of l5 amperes, and a capacity of 75 amperes for short periods of time such as thirty seconds, will pass the full 75 amperes, or will cut it oi, or will pass any intermediate amount of current in accordance with the-intensity of the light to which the tube is subjected.

It is among the objects of this invention therefore:

To provide generally an improved photo-electric tube;

To provide a photo-electric tube responding .to the action of light to pass therethrough current of great amperage, limited only by the permissible temperature rise of the tube; y

To provide a tube of .the rectifier type having a maximum current carrying capacity between the anode and cathode, and rendered responsive in an improved manner to the action of light, to pass current in varying amounts from small currents to said maximum current when illuminated by' light in corresponding degrees of intensity;

To provide a photo-electric tube having an improved mode of operation;

To provide an improved construction -of rectifier tubeA of the gas-filled, hot cathode type, adaptable, in an improved manner, to respond to the light as a photo-electric tube.

Other objects will be apparent to those skilled in the art to which our invention appertains.

Our invention is fully disclosed in the follow- I ing description taken in connection with the active material, nor in fact upon light-sensitivel properties as such, of the coatings within the envelope. The amperage flowing through the tube in response to the action of light, being at its maximum, equal to the discharge amperage capacity of the tube as a rectifier, is many times greater than the electron flow which could possibly be emitted from the said coatings considered as light sensitive coatings, even ifsuch light sensitive coatings were 'of the maximum possible area that could be contained within the envelope. The phenomenon seems to depend upon the joint action (a) of the grid in normally preventing electron flow between the cathode and anode, or in causing it to flow, as thev case may be; and (b) of the coating in wholly or partially inhibiting the said action of the grid when exposed to light.

The phenomenon may be electro-static in c haracter. When the outside band grid is utilized as described, we believe that it creates an electrostatic charge or field within the envelope, or on the inner wall thereof, the glass wall of the envelope functioning in the nature of the dielectric element of a condenser; and that it is this 75` companying drawings, in which:

Fig. 1 is a front elevational AView of a tube embodying our invention and with a part of the envelope broken away to disclose internal parts of the tube;

Fig. 2 isa view to enlarged scale partly in longitudinal section nof a cathode of the tube of Fig. 1;

Fig. 3 is a view taken from the plane 3-3 of Fig. 2;

Fig. 4 is a view to reduced scale taken in the direction of the arrow 4 of Fig. 2;

Fig. 5 is a View in some respects diagrammatic illustrating the internal construction of the cathode of Fig. 2;

Fig. 6 is a cross-ection'al View taken from the plane 6-6 of Fig. 2;

Fig. 7 is a View in general similar to Fig. 1

but illustrating a modification;

Fig. 8 is a fragmentary View taken in the direction of the arrow 8 of Fig. 7, illustrating apart of the envelope of that figure and a window therein;

Fig. 9 is a fragmentary longitudinal sectionalI view of a part of the envelope of Fig. 7;

Fig. 10 is a view similar to Fig. 1, but illustrating a further modification; l

Fig. 11 is a diagrammatic view illustrating an electric circuit system which may be employed `with the tubes of Figs. 1, 7 and 10.

Referring to the drawings, we have shown in able gas such as argon Vtherein at a predetermined pressure to be referred to.

In the upper end portion of the envelope I is an anode 8 electrically connected to an external terminal 9 in the usual manner. The anode may be of graphite or molybdenum, or carbon or carbonized nickel, or maybe of other materials such as are commonly used for the anodes of tubes of the hot cathode rectifier type.

i At is shown generally a cathode of the indirectly heated type. structurally it' comprises, see Fig. 2, a pair of posts and I2, mounted in and extending upwardly from the pinch 1 and spot welded to opposite portionsl of a main outer cathode cylinder I3 of nickel or other suitable metal. For convenience of assembling, th posts |I and I2 are in two parts, lower parts 19 and 80 mounted and sealed in the pinch and carrying sleeves 8| and 82 welded thereto, and the upperl parts, the posts proper and I2, are telescoped into the sleeves 8| and 82 to mount the posts on the pinch.

Within the cylinder I3 and co-axial therewith is an inner metal tube I4, see Figs. 5l and 6. A plurality of heater tubes I5, I6, I1, and I8 are disposed between the inner wall of the cylinder I3 and the outer wall of the inner tube I4, and spot welded to the tubes I3 and I4 at opposite points on the heater tubes. The cross-sectional form of the inner tube I4 is preferably polygonal, A,

although this is not essential, and it may be of square cross-section as shown, or of hexagonal or octagonal section, and the planar portions of such polygonal tube provide convenient means foi` positioning the heater tubes |5 to I8 and the outer tube I3 around `a common axis of the cathode, as illustrated.

A post I9 mounted in and extending upwardly from the pinch 1 has its upper end disposed in a socket r thimble 20, secured as by weldingv to a lower outer` sheet metal head 2| having an upwardly extending skirt 22 at its periphery. A lower inner sheet metal head 23, likewise pro'- vided with a peripheral skirt 24 rests upon the head 2| and is preferably spaced therefrom to reduce heat conduction to the-head 2| by means of pimples or bosses 25 pressed outwardly downwardly from the metal of the head 23 and resting upon the head 2|.

l Perforations are provided in the heads through which the said posts I and I2 extend and thereby theheads are positioned relative to the posts.

The outer tube I3, inner tube I4, and heater tubes l |5 to I8, rest uponthe inner head 23 or terminate adjacent thereto, and the head 2| preferably rests upon the upper ends of the sleeves 8| and 82 to further .support the heads and tubes.

An upper head 2B is provided having a large central perforation 21 and a downwardly extending periphery skirt 28 secured to the upper end portions of the posts II and i2 by tongues 29- 75 28 bent upwardly from the periphery of the perforation and spot welded to the posts Il and |2 example as lava, are provided, resting upon the lower heads 23 and 2| respectively, and axially centered by engaging within the skirts 24 and 22 respectively of the lower heads.` At their upper ends the heat insulating shield 3| is engaged within the peripheral skirt 28 of the upper head 28 and the shield 30 is positioned by tongues 32 bent downwardly from the head 26. The inner heat shield 30 is.spaced from the tube I3, and the outer shield 3| is spaced from the inner shield thereby providing heat-insulating air spaces therewithin.

Below the cathode proper thus constructed, a ring 33 is supported by being welded to a post 34 mounted in the pinch. Heating filaments 35--36--31--38 of helical form are provided axiallyof' and within the heater tubes I5 to I8, their lower end s being extended axially and spot welded to the ring 33 and their upper ends being extended axially and spot welded to tongues 39 bent upwardly from the upper head 26 at the periphery of the perforation 21.

A heat reflector 48 of nickel or like material and in the form of a disc, is mounted above the cathode proper by tongues 4|-4I bent downwardly from opposite edges thereof and spot welded to the upper ends of the post and I2, preferably through the tongues 29.

The reflector reduces radiation axially away from the cathode, and together with the heat insulation eifected'by the shields 30 and 3| reduces the radiation of heat and enables the filaments 35 to 38 to maintain the desired temperature of the cathode `at the expenditure of correspondingly less wattage.

By the construction above described a large sheet metal cathode surface area is provided, and this surface area is covered with a coating of thermionic material such as barium or strontium carbonate or a mixture thereof, which, when the cathode surfaces are heated in the process of evacuating the tube as is customary, is converted into strontium or barium oxide or a mixture thereof.. `This oxide coating of thermionic material is shown in Fig. 6 at 42, on the inner wall of the outer tube I3 and at 43 on the outer walls of the heating tubes l5 to I8 and at 44 on the outer wall of the inner tube I4 and also at 45 on the inner wall of the tube I4.

An electric circuit to heat the filaments is provided from a wire 46 to the post 34, see Fig. 2, to which is connected the ringv 33, thence through all of theiilaments 35 to 38 in parallel, to the upper head 26 and thence through the, post Il and out by a wire 41.

A getter such` as that referred to is shown at 83, Fig. 1, mounted ona wire 84 welded to a sleeve such as the sleeve 82.

The main circuit through the tube is from the anode connection 9 to the anode 8, through the gap as a discharge arc to the cathode outer tube I3 and thence by post I2 to a wire 48.

The wires 46, 41 and 48, shown best in Fig. 2, are, as will be understood from prior tube practice, connected to the insulated prongs 4, 5 and 6 of the other figures, for example Fig. 1.

The tube as above `described may be considered as a rectifier tube having a well known mode of operation which is, that the filaments heat the the anode is positive; and the electric current being considered, conventionally, as flowing from the anode to the cathode in the nature of a space discharge, and in amount depending upon the external resistance in the circuit.

A grid 49 in the .form of an external band-grid upon and outside of the envelope I is provided and it may be variously constructed. It may ne in the form of a separate metal detachable Wire or band of metal; or a band of metal mesh; but preferably we provide a band which in effect is sealed into the material of the outer wall of the envelope. The preferred process for applying such a band-grid, is that used in ornamenting glassware with bands or the like of platinum. A so-called liquid platinum is painted in the form of a b and on the outer Wall of the envelope, and over anoutwardly extending nipple 58. The glass and the band are then heated and the band fuses into the glass surface under the band, having finally the appearance of being a part of the glass. A band thus made is conductive, and a terminal 5I is soldered or otherwise mounted on the nipple by which electric connection can be made to the grid.

The grid is shown as disposed between the cathode and anode, which is its preferred position.

With .a tube constructed as above described, and in operation :as described, negative energization of the grid at a suitable potential will prevent flow of discharge current through the tube, and lower degrees of energization will permit the flow in inversely corresponding amperage.

When alternating potential is impressed upon the anode and cathode, the ow of current occurs only during those half waves in which the anode is positive, and even without energization of theA grid, is automatically interrupted in each half cycle in which the anode is negative; and therefore with alternating current, such a tube admits of control of the effective amperage flowing, by suitable energization of the grid, inasmuch as the grid can at any time be energized to cut o the fiow of current by preventing its-starting on the next succeeding half cycle; or can control the effective amperage by delaying the time of starting in each positive half cycle. Also if the grid be energized to a degree beyond that at which it completely cuts off or prevents current flow, the current will be caused to flow at such super grid energization, and by reducing or raising this super energization, the effective amperage flow may be conversely increased or decreased or cut of. Because of the greater usefulness of the tube with alternating current as thus indicated, it will be considered herein only in such usage.

A more stable and otherwise satisfactory con- 'trol of the amperage flowing through the tube `and 41.

on the grid at this phase displacement. We have found that a suitable phase displacement is approximately 135 degrees lag of band grid negative potential behind the anode positive potential.

In Fig. 11 is illustrated a representative circuit for eecting this type of control with a. tube such as is described above. In this figure' at I is shown the envelope, at 8 the anode, at 49 the grid, at II and I2 the posts supporting the cathode I3 to I8, heated by filaments 35 to 38.4

Supply mains 52 and 53 energize the primary 54 of a transformer, the secondary 55 of which supplies alternating current at a suitable voltage, such for example as ve volts, to the above described heating circuit comprising the wires 46 The supply mains also energize the primary 56 of a transformer having a secondary 51 connected in a loop circuit with a resistor 58 and a condenser 59, the upper end of the resistor- 58 being connected to the supply main 52 by a resistor 58. 'I'he condenser 59 may be adjusted to cause the potential on the grid 49 to be out of phase with the potential on the anode 8 as described and at this fixed phase displacement, which as stated above, is preferably of the order of 135 degrees behind the anode potential, the actual potential on the grid 49 may be adjusted by the adjustable connection 62.

For a rectifier as described above having a continuous main lcurrent capacity of 21/2 amperes, the capacity of the condenser 59 may suitably be .019 micro-fared, and the resistance of the resistor may suitably be of the order of 150,000 ohms, and the voltage across the resistor, provided by the transformer secondary 51, may suitably be 600 volts for supply mains at 110 volts,` 60 cycles. As stated above, with the fixed phase displacement referred to, the grid connection at 62 may be adjusted from zero potential at which the full 21/2 amperes will ow in the main load circuit from the anode to the cathode of the tube, and if the potentialon the grid 49 be adjusted to raise it, the effective amperage in the load circuit will be decreased; and at approximately 450 volts on the grid 49, the main current will be completely cut o; and if the potential on the grid 49 be adjusted to raise it to a super potential v hereinbefore, when the envelope is evacuated by the usual process which we may employ, some' of the heated thermionic coating is evaporated and deposited on the inner surface of the envelope in a thin film, and the getter when flashed also deposits a lm on the tube Wall. A lm is indicated in Fig. 1 by the dotted line 63, and this may be considered as the thermionic film, or the getter film, or both.

The photo-electric property of the tube, to which thisspeciiication is particularly directed,

vis brought into action by two methods. The first method is by energizing the grid 49 with a negative potential preferably out* of phase with the potential impressed upon the anode and cathode as described and preferably just sufllcient to prevent the ilow of discharge current as described; so that considered as a rectifier tube, the tube is normally in the condition to prevent current flow. If now, light is caused to illuminate either the thermionic coating on the cathode or the nlm 63 on Vthe inner wall of the envelope (whether it be the part composed of thermionic material or the part deposited by the getter or both) the inhibitingr action of the grid is in itself inhibited,

and the tube passes current betweenthe anode' lamps. In such cases, `we prefer to employ anenvelope such as that shown in Fig. 7. This envelope is opaque except for a small transparent window 1U, and the controlling light is provided by a lamp 1|, reflector 12 and shutter 13 directing a pencil of light toward and through the and cathode. The amount of the current which thus flows is directly commensurable with the `degree of intensityof illumination of the thermionic material, or of the film, and if the illumination be suiciently intense, the tube will pass amperage of current up to its full capacity, de-

f pending upon the resistance of the external load circuit, and if the illumination is decreased the amperage ilowing through the tube decreases commensurably therewith, and if the illumination is entirely removed the current againceases to flow.

In the second method of bringing into action the photo-electric property of the tube, the grid 49 is energized with a. super negative potential, high enough to be beyond the potential at which current ow is prevented, and at this super potential current normally flows through the tube, the greater the super potential the greater the current and vice versa. The grid is therefore adjusted to a super potential at which the maximum current that is wanted will normally now, this maximum having of course a top limit at the discharge capacityof the tube. If now light is caused to illumine either of the three coatings referred to, or several of them, the action of the grid in causing the maximum current flow is thereby inhibited and the current flow is cut off or is reduced inversely commensurably with the degree of intensity of the illumination.

As will now be apparent, by the aforesaid first method of operation, the discharge current amperage increases from zero to higher values (up to the full discharge 'capacity of the tube) with increasing intensity of light, the flow of currentbeing directly commensurable with the light; and by the aforesaid second method of operation the discharge current decreases from a high value (a value determined by the degree of super gridenergization) down to zero with increasing intensities of light. the flow of current being inversely commensurable with light.

So far as we are aware in no prior photoelectricV tube does the current vary inversely with light; intensity. u

- We have found that the response of the tube. to `light is sensitive, and that `the light from an ordinary 50 watt commercial lamp at a distance of several feet from the tube and directed upon the tube by `a reflector is sufficient to cause the tube to respond and pass (or cut oil, as the case may be) its full capacity of current.

In Fig. 1, `we have shown at 64 a source of light directed by a reflector 65 upon the coating of the oathode I0, through a shutter 65, by which shutter the intensity of the incident illuwindow which pencil of lightmay be modified or interrupted by movement of the shutter. The pencil of light passing through the window falls upon avlm 14 provided on the inner wall of the envelope, the lm, as will be apparent, receiving no light except that of the pencil. In this gure,

we have illustrated for the nlm 14, a coating of predetermined area and shape, which has been deposited upon the inner wall of the envelope intentionally by distillation or other well known process, and disposed opposite the transparent window in alignment therewith and with the pencil of light.

The envelope of this figure may be rendered opaque by any suitable process, 'but we prefer to make the envelope initially of transparent` glass, as at 15, and then to superimpose thereon a layer of opaque glass, as at 16, fused to the underlying transparent layer, leaving uncoated the transparent window 10. The film 14 is disposed so that the minimum of shadow will be thrown thereon by the parts within the envelope which lie in the path of the ray of light entering the Window. l

As an alternative arrangement,` the envelope may be made oi transparent glass and covered inside with lamp black or other opaque material except for uncovered portions for the window and the coating. e

In Fig. 10, we have shown a modification which may be incorporated into the form of Fig. 1, or of Fig. 7. Here, the heat shields 30 and 3| of the form of Fig. 1, have been omitted, and the exterior surface of the cathode tube I3 is also coated with therrnionic material, as at 11, Fig. 10, and

, mination may be controlled; and at 61, 68- and functions in the operation of the tube as a rectifier, and the ray of light to operate the tube photo-electrically is directed upon this coating, as illustrated, under the control of a shutter 18.

As mentioned hereinbefore, rectifier tubes of the gaseous discharge type are known containing a gas such as argon in the envelope. In the above described tube, we also prefer to employ, as stated, a gas such as argon, but we have found that the pressure of the gas within the envelope when the tube is to be used for its light responsive properties described must be taken into account. For any pressureutilized, the grid energization should correspond if the optimum photoelectric effect is wanted. If a low gas pressure is used, the grid voltage used to normally prevent current flow may be and should be lower and vice versa.. At the higher gas pressures and corresponding higher grid voltage as well as at the lower pressures and corresponding lower grid voltage, the above described photo-electric action is present, but for a given maximum light intensity the maximum ow of current decreases as the pressure and grid voltage increase and also as they decrease. `It follows that there is an intermediate optimum pressure (and corresponding grid voltage) and we have found that for 69, we have shown `a similar arrangement vof "argon gas, which we prefer to use, this optimum f eilect according to the flrst method, by energizing the grid negatively at a potential which just prevents main current ow. This is the preferred condition when it is desired that the main current flow is to be cut of! entirely by cutting oil? the illumination. We have found that lf the grid be energized suillciently to permit a reduced or minimum main current flow through the tube, then, in response to the action of light, the tube will pass more current than this minimum, when illuminated as described; and ii the illumination be removed, the current will drop back to the said minimum value, and our invention contemplates the control of the main current in this manner. Likewise in the second method of operation our invention contemplates a super grid energization which, in the absence of illumination, will cause the tube to pass a desired maximum current.

We have referred hereinbefore to shutters to control the intensity of the illumination of the tube, and such shutters are representative of objects of any kind which may be moved into position to intercept or change the intensity of the used in multiple back-to-back arrangemen, pass a full wave of alternating current.

We claim:

1. 'I'he method of controlling the current amperage in an electric circuit having connected therein the anode and cathode of a rectifier-type space-discharge electronic tube comprising a control electrode and containing light-responsive 4material in the tube envelope. which includes terial to lightand determining theamperage of illumination, whereby the main current ow lizing a negative grid energized out of phase with y the positive anode and having the grid potential adjusted by a rheostat, it is to be understood that' our invention may likewise be practiced by a sys-l tem which adjusts the phase displacement of the grid energization with respect to the anode potential.

It is believed that these alternative methods of practicing our invention will be understood from the more complete-description of the preferred method without further illustration or description herein.

the current by the intensity of the light, independently of the value of said electrical potential. 2. The method of controlling the 'current amperage in an electric circuit having connected' therein the anode and cathode of 'a rectier-type amperage independently of the value of said electrical potential, by subjecting the light-responsive material to light at a corresponding preselected intensity.

3. 'I'he method of controlling the current amperage in an electric circuit having connected therein the anode and cathode of a rectifier-type y space-discharge electronic tube comprising a control electrode and containing light-responsive material in the tube envelope, which includes subjecting the anode and cathode to electrical potential suilicient to cause discharge current to ow in the tube and circuit but normally preventingI current ilow by energization of the control electrode, causing discharge current to flow by subjecting the light-responsive material to light,

and causing the current to vary by varying the intensity of the light.

As referred to hereinbefore, the tube illustrated and described herein, apart from its photoelectric property, is a tube of the rectier class, the amperage of the discharge through which may be controlled and varied by controlling the grid `voltage (or its phase relation to the -anode voltage).

The tube of this application considered as a Arectiiier tube constitutes the subject matter of to change by subjecting the light-responsive ma- Y terial to light.

5. The method of controlling the current amperage in an electric circuit having connected Atherein the anode and cathode of a rectier-type space-discharge electronic tube cc-nprising a control electrode and containing light-responsive material in the tube envelope, which includes subjecting the anode and cathode to electrical potential suiiicient to cause a normal value of discharge current to ilow While concurrently energizing the control electrode to maintain the current ow in the circuit at a lower value less than `the normal value, and causing the lower value to increase by `subjecting the light-responsive ma-` terial to light. l

6. The method of controlling the current amperage in an electric circuit having connected therein the anode and cathode of a rectifier-type space-discharge electronic tube comprising a control electrode and containing light-responsive material in the tube envelope, which includes subjecting the anode and cathode to electrical potential sufficient to cause a normal value of discharge current to flow While `concurrently energizing the control electrode to maintain the current ilow in the circuit at a lower value less than the normal value, and causing the lower value to increase by subjecting the light-responsive material to light, and limiting the amperage of the increased Value by limiting the intensity of the light.

7. 'Ihe method of controlling the current amperage in an electric circuit having connected therein the anode and cathode of a rectifiertype space-discharge electronic tube comprising a control electrode and containing light-responsive material in the tube envelope, which includes subjecting the anode and cathode to electrical potential suflicient to cause a normal value of discharge current to flow while concurrently energizing the control electrode to maintain the current flow in the circuit at a lower value less than the normal value, and causing the lower value to vary by subjecting the light-responsive material to light of varying intensity.

8. The method of controlling the current amperage in an electric circuit having connected therein the anode and cathode of a rectifiertype space-discharge electronic tube comprising a control electrode and containing light-responsive material in the tube envelope, which includes subjecting the anode and cathode to electrical potential suilicient to cause a normal value of discharge current to flow while concurrently energizing the control electrode. to maintain the current flow in the circuit at a lower value less than the normal value, and causing the lower value to increase and attain a preselected amperage by subjecting the light-responsive 4material to light ata corresponding preselected intensity. y

9. The method of controlling the current amperage in an electric circuit having connected therein the anode and cathode of a rectifier type space discharge electronic tube comprising a control electrode and'containing light-responsive material in the tube envelope, which includes: subjecting the anode and cathode to electrical potential suiilcient to cause a normal discharge current to flow while concurrently energizing the control electrode to a greater degree than that which would be suicient 4to prevent current ow and thereby causing current to flow at a lower value less than the normal value; and causing the lower value to decrease by subjecting the light-responsive material to light.

current to ilow while'concurrently energizing the control electrode to a greater degree than that which would be sumcient to prevent current flow and thereby causing current to flow at a value less than the normal value; and causing the discharge current dow to cease by subjecting the light-responsive material to light.

11. The method of controlling the current amperage in ank electric circuit having connected therein the anode and cathode of a rectifier type space discharge electronic tube comprising a control electrode and containing light-responsive material in the tube envelope, which includes: subjecting the anode and cathode to electrical potential sufficient to cause a normal discharge current to flow While concurrently energizing the control electrode to a greater degree than that which would be suflicient to prevent current flow and thereby causing current to flow at a lower value less than the normal value; and causing the lower value to decrease to a preselected value by subjecting the light-responsive materialto light at a corresponding preselected intensity.

12. The method of controlling the current amperage in an electric circuit having connected therein the anode and cathode `of a rectifier type space discharge electronic tube comprising a control electrode and containing light-responsive material in the tube envelope, which includes: subjecting the anode and cathode to electrical potential sufficient to cause a normal discharge current to flow while concurrently energizing the control electrode to a greater degree than that which would be sufficient to prevent current iiow and thereby causing current to flow at a lower value less than the normal value; and causing the lower value to vary by subjecting the lightresponsive material to light of varying intensity.

13. The method of controlling the current amperage in an electric circuit having connected therein cthe anode and cathode of a rectifier-type space-discharge electronic tube comprising a control electrode and containing light-responsive material in the tube envelope, which includes subjecting the anode and'cathode to electrical potential sufilcient to cause a normal value of discharge current to ow in the tube and circuit while concurrently preventing the current flow from attaining the normal value by energization of the control electrode, and subjecting the lightl0. The method of controlling the current amperage in an electric circuit having connected therein the anode and cathode of a rectifier type space discharge electronic' tube comprising a control electrode and containing light-responsive material in vthe tube envelope, which includes: subjecting the anode and cathode to electrical potential sufficient to cause a normal discharge responsive material to light to cause a flow of discharge current directly commensurable with the intensity of the light.

14. The method of controlling the current arxi-v perage in an electric circuit having connected therein the anode and cathode ora rectifier-type space-discharge electronic vtube comprising a control electrode and containing light-responsive material in the tube envelope which includes: subjecting the anode and cathode to electrical `potential sumcient to cause a normal value of discharge current to flow in the tube and circuit while concurrently preventing the current ilow from attaining the ynormal value by energization of. the control `electrode and subjecting the light responsive material to light to cause a flow of discharge current inversely commensurable with the intensity of the light.

' PALMER H. CRAIG.

LESTER C.- HERMAN. 

